This proposal requests support for a Keystone Symposia meeting entitled Mechanisms of Whole Organ Regeneration, organized by Alejandro Sanchez Alvarado, which will be held in Breckenridge, Colorado from April 1 - 6, 2012. The regeneration of organs and organ systems after injury is widely, but unevenly, distributed among animals. Why organ regeneration is not shared by all animals, and whether mechanisms may or may not be conserved among those animals that can regenerate remain open questions. In recent years, the use of a wider range of model organisms and an increasing ability to use genetic tools to study regeneration has spurred significant progress in our understanding of animal regenerative biology. This meeting aims to delineate the molecular and cell biological basis of regeneration by highlighting, comparing and contrasting the differences and similarities in regenerative capabilities and mechanisms among diverse animal species. How these biological findings may inform regenerative medicine and stem-cell biology and therapeutics will be considered and discussed. Opportunities for interdisciplinary interactions will be significantly enhanced by the concurrent meeting on Regenerative Tissue Engineering and Transplantation, which will share an opening and closing keynote address as well as two plenary sessions with this meeting.